Current internal combustion engine cylinder deactivation strategies are primarily based on the requested propulsion torque at the current vehicle operating conditions, and are used to improve fuel economy. Internal combustion engines have an order in which each piston located in each cylinder is scheduled for firing. In using a cylinder deactivation strategy, cylinders are either scheduled for combustion or deactivation, depending on the engine torque demand, NVH (noise, vibration and harshness), and vehicle/engine constraints. This approach applies to conventional fixed-mode cylinder deactivation systems (e.g., changing between eight active cylinders and four active cylinders, or changing between four active cylinders and two active cylinders), or multi-mode cylinder deactivation systems, in which any number of cylinders in a given engine cycle can be deactivated or fired to meet the engine load demand. In all of these systems, future knowledge of the vehicle operating conditions or vehicle environment is not accounted for or included when scheduling cylinder deactivation (or individual cylinder firings). This typically leads to a suboptimal powertrain fuel efficiency improvement. This is particularly true if frequent changes in the required engine load demand and changes in the upcoming vehicle driving conditions lead to unnecessary cylinder deactivations or potentially poor system response when attempting to reactivate (i.e., fire) some or all of the engine cylinders. A vehicle utilizing engine cylinder deactivation for fuel efficiency gains may encounter these drawbacks in various situations, including, but not limited to: heavy traffic driving, traffic light approaches, road curvatures, road grades, and general vehicle deceleration.
One example of these drawbacks may occur where a vehicle is driven on a road with one or more curvatures. In this instance, a typical engine cylinder deactivation strategy frequently deactivates and reactivates the cylinders as the driver tips in and out (i.e., applies and releases) the accelerator and brake pedals while negotiating a curve. This is to be expected in a conventional cylinder deactivation strategy as current engine load demand changes. This irregular engine cylinder deactivation, or “hunting,” may have a negative effect on drivability and fuel efficiency/emissions. One reason these negative effects occur is that as cylinders are fired for reactivation, in particular for a fixed-mode cylinder deactivation system (e.g., changing from eight cylinders to four cylinders, and vice versa), ignition retard is typically used to prevent engine torque surges during the cylinder reactivation. In some engine cylinder deactivation strategies, deactivation hunting is prevented by means of an engine deactivation inhibit hysteresis logic, which prevents further deactivations when the time since the last deactivation was too short. This may lead to fuel efficiency gains that are not realized, since the cylinder deactivation becomes inhibited while preventing hunting.
Accordingly, there exists a need for an optimized engine cylinder deactivation strategy which improves fuel efficiency based on either or both of a combination of vehicle telematics and autonomous driving strategies.